System using counter tube coder



5 Sheets-Sheei'. 1

Imam/70x2 mxvbim o zEbmJmw mbmm Q5 c. F, ANDERSON SYSTEM usmc COUNTERTUBE CODER April 21,v 1959 Filed June 27, 1955 United States PatentSYSTEM USING COUNTER TUBE CODER Carl F. Anderson, Los Angeles, Calif.,assignor to Packard-Bell Company, Los Angeles, Calif., a corporation ofCalifornia Application June 27, 1955, Serial No. 518,312

9 Claims. (Cl. 250-27) The present invention relates to improved meansand techniques for developing a series of time spaced pulses of thecharacter, for example, used in so-called IFF systems wherein it isdesired to produce different combinations of accurately spaced pulsesfor identification purposes.

Systems of this character have heretofore been proposed and theyinvariably include a so-called delay line as an essential part inachieving the spacing between pulses. One such prior art system involvesthe use of a pulse generator driving a delay line in such a manner thatthe total delay time which is achieved by the delay line is the totaltime required between the training pulses of the generated coded train.The number of taps required on the delay line is determined by thenumber of information pulses that are desired in the pulse train. Theinput, output and various taps on the delay line are fed to a codeconnecting network that has a common output, and used to display thecode train. A prior art system of this type has several disadvantages inthat (1) all of the pulses collected from the delay line are ofdiiferent amplitudes and shape; (2) the amplitude of the pulses in thetrain change as the pulses are switched in or out of the pulse train,i.e. code structure; and (3) it is a difficult and expensive job tobuild a multitapped delay line to the time tolerances required by such acoder.

Another prior art system involves the use of a sine wave oscillatorsynchronized with the line drive pulse generator with the oscillatorserving to produce the actual code pulses, with an accompanying delayline used to supply only timing information. However, certain problemsare involved in such system requiring relatively complex circuitry withits attendant probability of failure.

In accordance with the present invention, such prior art systems aregreatly simplified and made more reliable by the use of a so-called beamswitching tube which eliminates the necessity of a delay line.

It is therefore a general object of the present invention to provideimproved means and techniques for developing a train of pulses.

A specific object of the present invention is to provide a system ofthis character which avoids the use of delay lines.

Another specific object of the present invention is to provide a systemof this character which is relatively simple and reliable and which iseasily adjusted.

Another specific object of the present invention is to provide a systemof this character allowing convenient switching in and out of pulses ina coded train of pulses without affecting the amplitude or shape of theremaining pulses.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. This inventionitself, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may be best understood byreference to the following description taken in connection with theaccompanying drawings in which:

Figure l is a schematic representation of a system embodying features ofthe present invention;

Figure 2 is a transverse sectional view through a beam switching tubethat is connected in the circuitry illustrated in Figure 1;

Figure 3 represents additional circuitry which may be added to thecircuitry illustrated in Figure 1 for obtaining information pulses in1.45 microsecond steps;

Figure 4 represents the schematic form of another modification of thepresent invention; and

Figure 5 is a block diagram of the apparatus illustrated in Figure 1.

Briefly, the apparatus shown in Figures 1 and 5 functions as follows.

The positive trigger 10 applied to the input terminal A is applied tothe input grid of the bistable multivibrator code gate generator 12,causing it to change states. The resulting negative gate 14 appearing onthe connected cathodes of the tubes VIA and V1B is applied to thecontrol grid of the oscillator clamp tube V2A, causing a cessation ofthe space current through tube V2A. This sudden cessation of currentthrough tube V2A and the inductance L1 in the oscillator 16 causes theoscillator 16 to be shocked into oscillations which are sustained by theHartley type oscillator 16. The resulting sine waves have two phaseswhich are degrees apart and are applied to the control grids of tubesV3A and V3B which comprise a push-pull driver stage 20. The outputs fromthe driver stage 20 are applied to alternate connected grids, i.e. theodd and even grids, respectively, of a beam counter tube 22, which isillustrated in Figure 2.

As the potential of the grids of the counter tube 22 are progressivelylowered, the beam in the counter tube is caused to shift conduction fromtarget to target in rotation at a frequency that is two times thefrequency of oscillations developed in the oscillator stage 16.

Since the voltage developed on each tube target 22T is substantiallyindependent of each other, a switch 24, 25, 26, 27, 28 and 29 in serieswith a corresponding isolating diode 31, 32, 33, 34, 35 and 36,respectively, and placed between the differentiated target outputvoltage, and a common collecting resistor R17 allows the coding orselection of pulses to appear on a collecting resistor R17, so as todevelop a series of positive pulses, as represented by the pulse train40 and appearing on the output terminal 42.

The output of the beam tube target 22T1 is dilfereni tiated and thenapplied through the shut-01f pulse amplifier stage 46 to the connectedcathodes of the gate generator 12 to trigger the bistable gategenerator. This will cause .the gate generator to assume its originalstate, and the negative gate on the grid of oscillator clamp tube isthereby removed, allowing such clamp tube to conduct and to damp out theoscillations in the tank circuit including inductance L1. The counterthereby comes to rest with the beam on the last target and a circuit isthen ready to repeat its operation upon the application of anotherpositive trigger 10.

The tube 20 may be of the type supplied by Burroughs Corporation andknown as the type MO-10. The MO-lO is a magnetron type vacuum tube inwhich an electron beam is formed by crossed electric and magneticfields. A small permanent magnet (not shown) encloses the tube envelope22E (Figure 2) and supplies the latter field. The electron beamdesignated by the line 22B is formed between the central cathode 22C andone of ten circumferential positions, each of which contains the threeelectrodes: (a) spade 2281-22810, inclusive, to form and lock in thebeam, (b) targets 22T1-22T10, inclusive, to render a useful output, and(c) grids 22G1-22G10, inclusive, to switch the beam to the nextposit-ion.

The counter tube MO-lO is effectively a ten position electronic switchwith ten separate outputs with-in one small envelope. The MO-lO can bepreset to any one of its ten positions and the beam can remainindefinitely on one position or it can be advanced continuously at rateswhich exceed one megacycle.

The MO-10 as used commercially has an eleven stable state, namely aso-called clear condition in which the beam does not exist. One methodby which the tube can be placed in this clear condition is the momentaryinterruption of the spade and target positive supply voltages. From theclear condition the electron beam can be formed on a particular positionby momentarily reducing the voltage of the spade at that position to avalue approximately equal to the cathode potential. The circuitrydescribed in Figure 1 is now described in detail as follows. The inputterminal A is connected to the control grid of tube V1A through couplingcondenser 50. The grid of tube V1A is returned through resistance R2 toa source of 40 volts. The cathodes of tubes VIA and V1B are eachconnected through the output resistance R3 to the same 40 volt source.The anodes of tubes VIA and V1B are connected respectively throughresistances R4 and R5 to the +125 volt source. Condenser Cl connects theanode of tube V1A to the grid of tube V1B. Resistance R1 is connectedbetween the grid and cathode of tube V1B.

The clamp tube V2A has its anode connected directly to the +125 voltsource, its grid connected to the cathodes of tubes V1A, V1B and thecathode of tube V2A is returned to ground through the tapped inductanceL1, which is tuned by the adjustable condenser C2, connected in shunttherewith.

The oscillator tube V2B has its cathode connected to a 125 volt sourcethrough a pair of serially connected resistances 52 and 54, and ajunction of these resistances 52, 54 is connected through resistance 56to the control grid :of tube V213. The anode of tube V2B is connected tothe +125 volt source through resistance 58. Con-- denser 60 .couples thecontrol grid of tube V2B to the ungrounded terminal of the tank circuitof the oscillator which includes the elements L1 and condenser C2.

Two output are derived from the oscillator stage 16' and applied inproper phase to the push-pull drive-r stage 20. One of such two outputsis derived from the anode of tube V2B and is coupled by condenser 62 tothe control grid of tube V3A. A second one of such two outputs isderived from the oscillator cathode circuit and is applied to thecontrol grid of tube V313 through a net work which includes thecondenser 66 and adjustable resistance R6. Condenser 66 is connectedbetween the junction point of resistances 52 and 54, :on one hand, andthe control grid of tube V3B on the other hand. A-djust-' ableresistance R6 has one of its terminals connected to the tap on coil L1and its other terminal connected to the grid of tube V3B. R6 serves tocontrol the amplitude of the signal applied to the grid of tube V3B.

Tubes V3A and V3B have their cathodes intercon uected and returned toground through a common resist ance 70 which is shunted by the condenser72. The control grids of tube V3A and V3B respectively are connected toa 125 volt source through corresponding re sistances 74 and 76. Thecathodes of tubes V3A and V3B are connected to such 125 volt sourcethrough the common resistance 78. The anodes of tubes V3A and V3B areeach connected respectively to the corresponding outside terminals ofthe resistance R7 through corresponding resistances 80 and 82. Anadjustable tap on resist-- ance R7 is connected to the +125 volt source.The junction point of resistances 80 and R7 is connected to groundthrough the shunt connected resistance 84 and condenser 86. Likewise,the junction point between resistance R7 and resistance 82 is returnedto ground through the shunt connected resistance 88 and condenser 90.The anode of tube V3A is directly connected to each of the odd numberedgrids of the counter tube 22, while, likewise, the

anode of tube VSB is connected to each one of the even numbered grids oftube 22.

Each one of the spades of tube 22, namely the spades 2281-22810, isconnected to a positive 125 volt source through correspondingresistances 91-100. It is noted that the spade 2281 is connectible toground through switch S1, and that the spades 2259 and 22310 areinterconnected by resistance 99A.

One terminal of each of the target electrodes 22T1- 22TH) is connectedto the same 125 volt source through corresponding resistances 101110.The other terminals of targets 22T9 and 22T10 remain unconnected asshown. The other terminals of the targets 22T1--22T8 are con-- nectedrespectively to one terminal of the diode rectifiers 30-37 throughcorresponding condensers C5C12, the other terminals of the rectifiers 30and 37 being connected directly to the ungrounded terminal of the outputresistance R17, while the other terminals of the rectifiers 31- 36 areconnectible through corresponding switches 24-29 to such ungroundedterminal of the output resistance R17.

The pulses developed on the targets 22T1--22T8 occur at diflferent timesas indicated by the laterally spaced negative pulses 111118, appearingon the corresponding targets.

The negative pulse 111 is applied through condenser C3 and diode to thecontrol grid of the amplifier tube 46. The junction point of the diode120 and condenser C3 is returned to ground through resistance R8 to formof differentiating network. The control grid of tube 46 is returned toground through resistance 122 and the oathode of tube 46 is returned toground through resistance 124 which is shunted by condenser 126. Theanode of tube 46 is connected to a positive 125 volt source through theresistance 128. The anode of tube 46 is connected through condenser anddiode 132 to the cathode of tubes V1A, V1B. The junction point of theelements 130 and 132 is returned to a '-4() volt source throughresistance 134.

The operation of the circuit as shown in Figure l is as follows.

Before a positive trigger is applied to the point or input terminal A ofthe gate generator, the gate generator and the oscillator clamp areinitially subjected to the following conditions, namely, tube VlA is atcutofii and V1B is drawing maximum current. This is the normal steadystate condition, since tube V1 which comprises the sections VIA and V1Bis a monostable multivibrator and the grid resistor R1 of V1B isreturned directly to its cathode while the grid resistor R2 of V1A isreturned to -40 volts. The value of R3, in the cathode of tube V1, issuch that the DC. voltage at point B, i.e. at the cathodes of tubes VIAand V1B, is zero with respect to ground. Since the grid of theoscillator clamp tube V2A is connected directly to this point, it is atthe same D.-C. potential and tube V2A draws approximately 15milliamperes of current. Under these conditions, the cathode of tube V2A presents a low impedance across the tank circuit of the Hartleyoscillator V2B, thus preventing it from oscillating.

When a positive trigger voltage is applied to point A, tube VIA isturned on and tube V1B is shut off. The multivibrator remains in thiscondition, unless the circuit is influenced by an external voltage, fora period of time which is determined by the values of condenser C1 andresistance R1. The time constant C1R1 is set to be about 30microseconds, which is approximately the time required for one andone-half code trains.

Tube V1A draws less current than tube V1B because the plate resistor R4is larger in value than R5. Thus, the Voltage at point B becomesnegative with respect to ground. A negative pulse is produced in thismanner at the grid of tube V2A of sufiicient amplitude to shut off tubeV2A. The current which is drawn by tube V2A through the oscillator coilL1 is suddenly reduced to zero. The collapsing field in coil Ll sets upa shocked oscillatory condition in the tank circuit L1, C2. Theoscillation always starts in the negative direction since the energy inthe tank is reducing. Resistance R6 in the cathode circuit of tube VZBis adjusted to the point where tube V2B maintains the oscillations at aconstant amplitude. In other words, tube V2B supplies just enough energyto the tank circuit to overcome circuit losses.

Tube V2B is also used as a phase inverter. The cathode and plate outputsare adjusted for equal amplitudes by selecting the proper load valuesfor the two circuits.

Without a signal applied to the grids of the push-pull driver tube V3A,V3B, the resistance network in the plate circuit of tube V3 is designedso that approximately +30 volts with respect to ground is applied to theanodes of tube V3. This is done so that the grids of the beam switchingtube 22, which are directly connected to the anodes of tube V3, are atthe proper bias point. To make it possible to pull the plates of tube V3below ground and also to establish the proper operating point for tubeV3, the cathodes of tube V3 are returned to a negative voltage. The gridbias on tube V3 is set so that under no signal conditions the tube is ator slightly beyond cutoff. Since only the positive portion of the phaseinverted sine waves produce a change in the plate circuit of tube V3,the anode of tube V3A is the first pulled below ground,- followedone-half cycle by the anode of tube V3B. If the anodes of tube V3 areobserved simultaneously, their combined outputs appear as a full wave,rectified, sine wave. The anode of tube V3 is connected directly to allthe odd numbered grids and the anode of tube V313 is connected directlyto all of the even numbered grids of the beam switching tube, andbecause of the full-wave rectification mentioned above, the beamswitching tube steps to its progressive positions at twice the rate ofthe fundamental frequency of the oscillator.

When the coder is initially turned on, it is necessary to form the beamin the beam switching tube 22 on the proper spade. This is accomplishedby closing switch $1, a momentary contact switch, which is located atthe top of the spade load resistor network. This reduces the voltage onnumber one spade to zero and forms the beam in the number one position.

.When the large negative-going signal from the anode of tube V3A isapplied to the odd numbered grids of the beam switching tube 22, thestable condition existing at position one is upset and the beam moves toposition two. Immediately thereafter, the anode of tube V3B applies alarge negative-going signal to the even grids of the beam switching tubeand the beam moves to position three. In this manner, the beam isprogressively stepped around the tube. Since the beam switching tubewhich is used has ten positions and since the coder, as described,requires an eight-position'tube, it is necessary to make theten-position tube operate as if it were an eight-target tube. This isaccomplished by vconnecting together spades nine and ten through theproper resistance value. As the beam strikes each spade, the voltage onthe spade is decreased due to the current drawn by the spade through itsload resistance. As the beam strikes spade number nine, it does not finda stable condition since the voltage on, spade number ten is alsodecreasing because of the resistance that ties the two together. Thebeam, therefore, moves to position number ten. It does not stay in thisposition since all of the even numbered grids are still pulled belowground by the signal from the anode of tube V3B. In this manner, thebeam moves on to position number one. It is at this point that theprogress of the beam around the tube must be stopped since it has passedthrough all the required positions for generating a com.- plete pulsetrain. As the beam strikes each target, the voltage on the target isreduced for the same reason mentioned in connection with the spadevoltage. The leading edge of the negative pulse produced as the beamstrikes target number one is differentiated by condenser C3 and R8, andapplied through the coupling diode to tube V5. Tube V5 phase inverts andamplifies this pulse and applies it through the coupling diode to pointB. The effect of this positive pulse applied to point B is l) to forcethe monostable multivibrator back to its normal state which, of course,removes the negative gate from point B, and (2) to drive the grid oftube V2A into the positive region to cause the oscillator tube V2B tostop oscillating immediately. The coder now has completed one completecycle and is ready for the next trigger pulse.

The output or code pulses are generated and selected in the followingmanner.

The framing and information pulses are produced as the beam leaves eachtarget and not when the beam first strikes the target. Since the framingpulses and each code pulse are generated in exactly the same manner, thegeneration of the first framing pulse only is described. As the beamleaves target number one, the rising voltage on number one target isdifierentiated by condenser C5 and resistance R9. The resulting positivepulse is passed by the collecting diode 30 and appears across the commonload resistance R17. The information pulses are inserted or removed fromthe code structure by operation of the proper code selecting switches24-29.

The spacing between pulses in the output train 40 is controlled by theHartley oscillator tuning condenser C2 and resistance R7, the adjustablevoltage divider in the anode circuit of tube V3. By observing the first(framing pulse and the second information pulse (on an externallysynchronized oscilloscope), condenser C2 is set to obtain 5.8microseconds between the leading edges of these two pulses. The firstframing pulse and the first information pulse are then displayed on theoscilloscope, and resistance R7 is adjusted to obtain 2.9 microsecondsbetween the leading edges of this pair of pulses. Condenser C2 sets thefrequency of the Hartley oscillator, which controls the spacing betweeneven pulses and the spacing between odd pulses. Resistance R7 sets theswitching level between the odd and even grids of the beam switchingtube 22, and this controls the spacing between the odd and even pulses.Resistance R7 compensates for any pulse shape or amplitude variationbetween the outputs of tubes V3A and V3B.

Thus, using the circuit shown in Figure 1, any one of six informationpulses corresponding to switches 24--29 may be inserted in or removedfrom the pulse train which is bracketed by the first and last pulses,namely the framing pulses developed respectively from target one andtarget eight. These pulses, as indicated above, are separated by timeinterval of 2.9 microseconds. In order to decrease the time spacingbetween selectable pulses to 1.45 microseconds, the circuitry shown inFigure 3 is added to the circuitry shown in Figure 1 by makingadditional connections to the targets of tube 22, as indicated.

The pulses which are developed in Figure 3 are applied to the samecollecting or output resistance R17 which is identical to the resistanceR17 shown in Figure 1. In this case, all of the pulses developed inFigure 3 are delayed 1.45 microseconds by the delay line 202 so thatthese pulses fall between, in time, the pulses developed by theapparatus shown in Figure l.

The circuitry shown in Figure 3 includes seven selecting switches223-429, which serve to selectively connect the control grid of tube V5to a corresponding one of the targets one-seven of the beam tube 22through corresponding diodes 230-236 and through correspondingcondensers C25C31, which condensers are associated respectively with acorresponding resistance R29R35 to form a corresponding difierentiatin-gnetwork.

The tube V5 has its anode connected to a volt source and has its controlgrid returned to ground through resistance 240. 'Ilhe cathode of tube V5is connected to ground through the coil 202L of the delay line 202, andthe resistance 242. The delay line 202 includes the shunt capacitor 2020which may be the self-capacity of the coil 202L. The junction point ofthe delay line 202 and resistance 242 is coupled to the ungroundedterminal of resistance R17 through coupling condenser 244, which isconnected in shunt with resistance 246. Thus, when the circuitry shownin Figure 3 is added to the coder, information pulses are available in1.45 microsecond steps. The first framing pulse is fed to the grid oftube V through the first selecting switch which is closed. Such pulse isdelayed 1.45 microseconds by the delay line 292 in the cathode circuitof tube V5, and reinserted into the common code collecting network whereit becomes the first information pulse in the code structure. Eaclhsucceeding 2.9 microsecond pulse is delayed and reinserted into the codestructure in the same manner. The last training pulse developed ontarget eight is not fed through the delay circuit, since if it werereinserted, it would fall outside of the last framing pulse produced,using the apparatus shown in Figure 1. There are now thirteen selectableinformation pulses available, instead of the original six. Of course,all of the thirteen pulses do not have to be used, and any that are notrequired may be switched out of the circuit.

The circuitry shown in Figure 4 is able to accommodate two triggersources, both feeding information into a common beam switching orcounter tube 22, having the aforementioned targets one-eight. The gategenerators 12A and 12B are each exactly as the gate generator 12described in Figure 1, and the points or terminals A, B and C correspondto the terminals A, B and C in Figure 4. The terminals B and B are eachconnected to the control grid of the clamp tube V2A but, in this case,isolating diodes CR1 and CR2 are provided so that one gate generatordoes not trigger the other gate generator. Another slight modificationis that resisance R18 is connected between the control grid and thepositive source of voltage so as to again normally maintain the clamptube V2A conducting in its quiescent state. In this case the value ofthe resistance R18 is such that, under no-signal conditions, the gridcurrent drawn by the tube V2A through this resistance holds the grid oftube V2A at zero volts with respect to ground. The points A and B inFigure 4 have the same significance that they have in Figure 1, and itis noted that the point C is also designated in Figure 1 and is theoutput from the anode of tube VlB. The voltage on the points C and C isapplied in Figure 4 through corresponding coupling condensers 301 and302 to corresponding biased diodes CR3 and CR4, which diodes arenormally biased negatively so as to disable the code selecting network.In order to render such code selecting networks, either N or N in Figure4, it is necessary that positive voltage of sufficient intensity beapplied to the diodes CR3 and CR4, which are maintained at a negativepotential through resistances 303 and 304. Such enabling positivevoltage is derived from the gate generators 12A or 12B, as the case maybe. In other words, all of the input load resistances for the collectingdiodes in Figure 4 are removed from ground and returned to -40 volts.This voltage disables the collecting network until the 40 volts isremoved. When either one of the gate generators 12a or 12b, as the casemay be, receives a positive trigger, the positive pulse that isgenerated at point C or C is applied to the proper disabling circuit.The positive pulse applied allows the diode CR3 or CR4, as the case maybe, to clamp the disabling circuit to ground, and thus, the codecollecting network in question is ready for operation. The coder is nowable to reply with either of the two preset codes, depending on whichgate generator is triggered. The output of each code selecting network Nand N is applied to a common output resistance R17.

While the particular embodiments of the present invention have beenshown and described, it will be ob vious to those skilled in the artthat changes and modifications may be made without departing from thisinvention in its broader aspects and, therefore, the aim in the appendedclaims is to cover all such changes and modifications as fall within thetrue spirit and scope of this invention.

I claim.

1. In a pulse transmission system of the character described fortransmitting a series of pulses separated in integral fractions of timecorresponding to the periodicity of oscillations, an electronicswitching tube having a plurality of electrodes which are progressivelyswept by an electronic beam, a high frequency oscillator developing saidoscillation and coupled to said tube for moving said 'beam insynchronism with the oscillations developed in said oscillator, a commonoutput circuit, selectable switching means connecting a correspondingone of said electrodes to said common output circuit, second selectableswitching means coupled to a corresponding one of said electrodes, anddelay means interposed between said common output circuit and saidelectrodes.

2. In a pulse transmission system of the character described fortransmitting a series of pulses separated in integral fractions of timecorresponding to the periodicity of oscillations, an oscillatorproducing said oscillations, sequentially operated electronic switchingmeans operated in timed relationship with said oscillations, means foroperating said switching means through a cycle, said switching meanshaving a plurality of output circuits, a common output circuit, firstselectable switching means connecting a corresponding one of said outputcircuits to said common output circuit, a second set of selectableswitching means connecting said output circuits to said common outputcircuits, a first pulse responsive means for controlling said operatingmeans, a second pulse responsive means for controlling said operatingmeans, said first pulse responsive means, when energized, beingeffective to render only one of said selectable switching meanseffective to couple said output circuits to said com mon output circuit,and said second pulse responsive means, when energized, being effectiveto render the other one of said selectable switching means elfective tocouple said output circuits to said common output circuit.

3. In a pulse transmission system of the character described fortransmitting a series of pulses separated in integral fractions of timecorresponding to the periodicity of oscillations, electronic switchingmeans comprising a tube having a rotatable cathode beam engageable insuccession with a plurality of electrodes, an oscillator producing saidoscillations and coupled to said tube for producing movement of saidcathode beam in timed relationship with respect to the oscillationsdeveloped in said oscillator, pulse responsive means for initiatingoperation of said oscillator, said pulse responsive means includingmeans for assuring a predetermined phase of the first half one of theoscillations developed by said oscillator, and means coupled to one ofsaid electrodes for interrupting the oscillations developed in saidoscillator.

4. A system as described in claim 3 including a common output circuit,and selectable switching means between a corresponding one of saidelectrodes and said output circuit.

5. A system as described in claim 4 including a second set of selectableswitching means, delay means, and said second set of selectableswitching means and said delay means being connected between said outputelectrodes and said common output circuit.

6. In a pulse transmission system of the character described fortransmitting a series of pulses separated in integral fractions of timecorresponding to the periodicity of oscillations, a gate generatorhaving an input circuit responsive to a pulse for initiating a gatingvoltage, an oscillator producing said oscillations, a clamping circuitfor said oscillator and coupled thereto for normally rendering saidoscillator ineffective to develop oscillations, said clamping circuitbeing coupled to said gate generator and responsive to said gatingvoltage, said clamping circuit being energized by said gating voltage toallow said oscillator to oscillate, an electronic switching tube havinga cathode beam movable in succession into engagement with a plurality ofelectrodes, means coupling said oscillator to said tube to move saidcathode beam in synchronism with the oscillations developed in saidoscillator, and means coupled between one of said electrodes and saidgate generator for terminating said gating voltage to thereby restoresaid oscillator to its normally non-oscillating condition.

7. A system as described in claim 6 including a common output circuitand selectable switching means connected between a corresponding one ofsaid electrodes and said common output circuit.

8. A system as described in claim 7 including second selectableswitching means, delay means, said second selectable switching means andsaid delay means being interposed between said electrodes and saidcommon output circuit.

9. In a pulse transmission system of the character described fortransmitting a series of pulses separated in integral fractions of timecorresponding to the periodicity of oscillations, an electronicswitching tube having a cathode beam movable in succession intoengagement with a series of electrodes, an oscillation network fordeveloping said oscillations and coupled to said tube for moving saidcathode beam in timed relationship with the oscillations developed insaid oscillator, means normally rendering said oscillation networkineflective to develop oscillations, at common output circuit, a firstset of selectable switching means interposed between said electrodes andsaid common output circuit, means normally rendering said first set ofselectable switching means ineffective to connect said electrodes tosaid common output circuit, a second set of selectable switching meansconnected between said electrodes and said common output circuit, meansnormally rendering said second set of selectable switching meansineffective to connect said electrodes to said common output circuit, afirst pulse responsive means for controlling said oscillation network, asecond pulse responsive means for controlling said oscillation network,means coupled between said first pulse responsive means and thefirst-mentioned rendering means for disabling the first-mentionedrendering means to thereby render said first selectable switching meanseffective to connect said electrodes to said common output circuit, andmeans coupled between said second pulse responsive means and the secondmentioned rendering means for rendering said second mentioned renderingmeans inefiective to thereby render said second set of selectableswitching means efiective to connect said electrodes to said commonoutput circuit.

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